Electrolytic manufacture of chlorates and perchlorates.



PATENTED MAY 12 I P. LEDBRLIN.

ELECTROLYTIC MANUFACTURE OFCHLORATES ANDPERGHLQEAT APPLIGAI'IO}! EILED JULY 11, 1902. N0 MODEL.

W1 T/VESSES:

YPIERRELEDIERYLIN, o CHEDDE, FRANCE. i

" PAT NT OFFICE.

i ELECTROLYTIC MANUFACTURE orcmenmts Am) PERCHLORATES.

- srnclmcsnoum in part of Letters Patent No. 727,813, dated. May 12, 1903. l

' Applioaition filedd'nly11,1902. Serial in, 115,240. on specimens.)

To all whom/it may concern: 'Be it known that I, PIERRE LEDERLIN, a citizenofthe Republic of France, and a resi dent of Ghedde, Haute Savoie, France, have invented'new and useful Improvementsin or Relating to the .Electrolytical Manufacture of Chlorates and Perchlorates, which invention is fullyset forth in the following specification.

The presentinvention relates to a new electrolytic treatment of alkaline chlorids in a solution of water, with the object of obtaining corresponding chlorates of an extremely high electrochemical yie1d,'almost equal to its theoretical figure. l

I have observed that whenever a neutral solution (originally neutral) of alkaline chlorid .is electrolyzed the gases. .which' are given off bythe electrolyte (a variable mixture of oxy- "gen and hydrogen gas produced by the'decomposition of water) possess a characteristic smell which indicates the presence of chlorin or of oxygenated orchlorinated components in the mixture.

- over, disclose precisely the presence of these l end of a snfliciently long time the alkalinity Med alkalifin'the body of the liquid- 4 is brought toia certain'strength and remains constant. I have proved that the strength of the liquid in caustic alkali corresponds in every case to the total amount of ;ch lorin given ed with the gaseous products generated-and that from. the moment at which the alkaline strength becomesconstant the disengagement of chlorin ceases, This being established, I have discovered that the diminution in the yield'of chlorate produced during the electrolysis, whichvcan always be observed, is solely due to the formation or appearance of liber- In order to'explain clearly, I will cite the following examples, in which all the conditions besides fth'ose. expressly indicated in each example are "exactly the samefrom one experiment to the other, (temperature, density,-and intensity of the current, volume, nature, forms, dimensions, and distance of the electrodes, &c.-:)

First example: Asolution of NaCl is elec- Chernical reagents, more-.

. trolyzed with anaddition of thirteen grams of NafirO, perliter and constantly maintained red by the'addition of diluted HOI, according to the indications of my Patent No. 693,035.

Under the's'e conditions the electrochemical yield of chlorate olsodium reaches, as shown.

in my Patent No. 693,035, 055 gram per am pore-hour, which would correspond to eightythree per cent. of the theoretical product,

(0.66 gram per ampere-hour,) and this indefii ,nitely, provided that the produced chlorate is periodically removed by refrigerating'the' and that the NaCl which is transformed is re solution, and thus crystallizing the chlorate placed and the liquid maintained constantly red by the addition of diluted H01, as indi cated in thepaten't. If the additionof HCl is sufiiciently maintained even, 0.61 gram can be obtained per ampere-hour. However, if in the course of theelectrolysis five grams ofv NaOH per liter are added to the electrolyte,

of which four grams are used to restore the bichromate to the state of neutral chi-ornate,

thus ,only leaving one gram of NaOH free per liter, the yield sinks and falls from this mo-f ment' to 0.4L grams of sixty-two per cent. of

the theoretical yield. When two grams of free NaOH are added, the yield falls weer gram, which is thirty-seven per cent of the theoretical yield. It can thusbe seen that the yield decreases in proportion as-the addition 1 of alkali is increased.

Secondexample: If, on the contrary, a neutral solution of NaOl is electrolyzed, (without anyaddition of chromates or bichromates,).it

will be observed that when the spontaneous increase in the strength of free alkali has be-' come constant the electrochemicalyield of chlorate has become very low and been found 1 to bed-34 gram per ampere-hon r, which would be fifty-one per cent of the theoretical yield; but if at this moment a quantity of diluted HCl is added sulficient to-neutralize the quau tity of iree alkali which in this moment remains in the liquid and from this moment the liquid is constantly maintained non-alkaline by the addition of the H01 corresponding to the quantities of freetalkali which tend to form theelectrochemical yield becomess'ud denly very high and. remainsindefinitely at about 0. 55 gram,which would be eighty-three per cent. of the theoretical amount, and it ioo 5 a one hundred and two grams of NaClO were -even rises to 0.65 grain, which corresponds to ninety-two per cent. of the theoretical value if the introduction ofdiluted HCl is continued sufficiently long.

, Third example: On electrolyziugasolution of NaCl with'a previous addition of one gram "of NaOH 'per liter-the electrochemical yield falls again below that which is obtained in startingjwi'th' an originally neutral solution (firstpart of Exam pie 2 above) and falls to O. 33 gram .corre'sponding'to fifty per cent. ofthe theoretical amount. If the addition of N aOH [amounts to two grams,-'the yield falls to 0.30

gram', corresponding to forty-five per cent. of.

the theoretical amount.

.These three examples show clearly the in- V juriousettect onthe yield of small quantities I or freejailkali in the electrolyte.

have also proved that the decrease of the electrochemical yield coinciding-with the appear ance of free alkali in t'he'liquid isby no means proportionate torthe actual loss of gaseous 'chlorin corresponding -to this quantity of free alkalh. In fact, according to Example 2;"i'zivenabove, beforeany addition of acid I obtained in, for i nstance, three hundred am- 6- eight grams.

pare-hours, while-the theoretical yield of NaClO would be one hundred and ninety- There is therefore a loss in the production of N aClO of ninety-six grams, corresponding to forty -nine' grams of NaCl. Therefore at the same time the total yield of O1 in the iodid-of-potassium tube is 3.5 grains, a quantity which represents only 5.8 grams of NaOl. The diminution of the yield of chlorate calculated in chlorid is thus much superior to the quantity of NaOl, cor-respondingto'the chloringiven off by the electro-' lyte. On the contrary, upon adding H01 during the -period of the'process, according to v of j N aCl.

' N aCl.

Example 2; one hundred and eighty three grams of NaClO are produced during a period of three hundred am pere-hours until the process stops, instead of one hundred and nine'ty-.

eight grams, (.thetheomttcal amount.) There is therefore a fall in production of fifteen grams of NaCIO corresponding to 6.7 grams At the same time the iodid-tube gives a total yield corresponding to 3.4 grams of chlorin,.corresponding to 5.6 grams of In this casethe loss in chlorin liberated and calculated in chlorin corresponds to eighty-three per cent. of the quantity (caltulated in chlorid) of whichthe yield in chlorate is reduced. Thus it is proved, first, that 'thefa'llinthe yield in chlorate in the electrolysis-of alkaline chloride in a neutral solution is solely due to the spontaneous appearance of small quantities of liberated alkali in the electrolyte; second, that this appearance comes from the disappearance of small quantities of jchl'orin from the body of the electrolyte and carried off in a gaseous form with the other gases coming from the electrolytic decomposition, (oxygen gas and, above all, hydrogen Moreover, I

electrolyte in which 'the anode and cathode gas;) third, thatin this case there is no propertion between this fall and this loss in chlorin. Since then I have soughtand discovered various means for preventing the production of harmful alkaline, and consequently for-attaining. indefinitely a yield which comes as alkali is alwaysprevented. The approximate proportions'of the neutral chromate and sa' line electrolyte (chlorid solution) maybe two' grams of neutralchromate to twenty grams of the saline electrolyte. In this manner, as shown in'my Patent No.'693,085, I'canse',owing to the acidity, the favorable property of chro mic acid to entirely and continually compen sate the cathodic reduction, which is one of the causes for the loss in the yield. Thus a yield of 0.55110 0.50 gram; per ampere-hour is.

obtained with 'NaCl, corresponding toeightyfour per cent. of the theoretical'yield, and thus by using indefinitely the same metal. cathodesand the sameliquids periodically 'roo deprived of theclilorate produced and re- .charged with chlorids corresponding to the quantity of the produced chlorate, while with the neutral chromate without the use of acids under the above-defined conditions-the yield falls to thirty-six grams, corresponding at the most to fifty-five per cent. of the theoretical amount, and remains at that indefinitely.

The accompanying drawing shows av sectional view'of an ordinary electrolytecell: which may be used in carrying out the process herein described, A being an anode, B a. cathode, and O the vessel for containing the are submerged.

...I claim v j A method forthe manufacture at-a high constant yield of chlorates'a'nd perchlorates by the electrolysis of a chlorid solution with the previous addition of acorresponding neutral chromate, consistingin maintaining the electrolyte during the electrolysis in a nonalkaline state by the addition of hydrochloric acid. r Y

' In testimony whereof. I have signed .this specification in the presence of two subscribing witnesses.

PIERRE LED'ERLIN.

Witnesses:

EMILE LEDRET, EDWARD P. MA0LEA-N.

r i m 

